Re: [Patch, AArch64] Fix shuffle for big-endian.

[Tejas Belagod]

Richard Henderson wrote:

On 02/21/2014 08:30 AM, Tejas Belagod wrote:

+      /* If two vectors, we end up with a wierd mixed-endian mode on NEON.  */
+      if (BYTES_BIG_ENDIAN)
+       {
+         if (!d->one_vector_p && d->perm[i] & nunits)
+           {
+             /* Extract the offset.  */
+             elt = d->perm[i] & (nunits - 1);
+             /* Reverse the top half.  */
+             elt = nunits - 1 - elt;
+             /* Offset it by the bottom half.  */
+             elt += nunits;
+           }
+         else
+           elt = nunits - 1 - d->perm[i];
+       }

Isn't this just

  elt = d->perm[i] ^ (nunits - 1);

all the time?  I.e. invert the index within the word,
but leave the word index (nunits) unchanged.

Here is a revised patch. OK for stage-1?

Thanks
Tejas.

2014-04-02  Tejas Belagod  <tejas.bela...@yahoo.com>

gcc/

        * config/aarch64/aarch64.c (aarch64_evpc_tbl): Reverse order of elements
        for big-endian.
diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
index e839539..d30b79c 100644
--- a/gcc/config/aarch64/aarch64.c
+++ b/gcc/config/aarch64/aarch64.c
@@ -8129,7 +8129,15 @@ aarch64_evpc_tbl (struct expand_vec_perm_d *d)
     return false;
 
   for (i = 0; i < nelt; ++i)
-    rperm[i] = GEN_INT (d->perm[i]);
+    {
+      int nunits = GET_MODE_NUNITS (vmode);
+
+      /* If big-endian and two vectors we end up with a wierd mixed-endian
+        mode on NEON.  Reverse the index within each word but not the word
+        itself.  */
+      rperm[i] = GEN_INT (BYTES_BIG_ENDIAN ? d->perm[i] ^ (nunits - 1)
+                                          : d->perm[i]);
+    }
   sel = gen_rtx_CONST_VECTOR (vmode, gen_rtvec_v (nelt, rperm));
   sel = force_reg (vmode, sel);